Operating Machine, in Particular a Motor-Driven Pump with an Axial Motor Arrangement

ABSTRACT

The present invention refers to an operating machine, in particular a motor-driven pump with an axial motor arrangement, comprising a rotor assembly ( 18 ) and a stator assembly ( 7 ). The rotor assembly ( 18 ) includes an impeller ( 4 ) and a permanent-magnet rotor ( 5 ) firmly associated to the impeller ( 4 ). The stator assembly ( 7 ) includes a single multipolar stator ( 8, 9, 10 ) interacting with the rotor ( 5 ) to impart a rotary motion to the impeller ( 4 ) along an axis (A) perpendicular to the rotor ( 5 ). The rotor assembly ( 18 ) is rotatably supported by a flange ( 6 ) adapted to separate the rotor assembly ( 18 ) from the stator assembly ( 7 ). Guide means ( 16, 17 ) are provided between the rotor assembly ( 18 ) and the flange ( 6 ) to guide the rotary motion of the impeller ( 4 ) about the axis (A).

The present invention refers to an operating machine, in particular a motor-driven pump with an axial motor arrangement, which comprises a chamber where there is arranged a concentric impeller rotating about an axis; the concentric impeller is provided with vanes adapted to impart a kinetic impulse to a working fluid—either in a liquid or a gaseous form—at the pump outlet.

When designing operating machines of the above-noted kind for use in a variety of industry sectors, such as for instance in the sector of home appliances including clothes washing machines and dishwashing machines, a major factor that needs to be taken into due consideration is the volume occupied by the machine: this is a parameter which has to be kept as low as possible, and even progressively reduced, so as to render the machine more and more integrated in the structure which has to incorporate it. This has the aim, on the one hand, to achieve a larger free volume available inside said structure and, on the other hand, to allow the operating machine to be used in applications where available built-in space for accommodation of such machine gives rise to serious dimensional constraints.

Another particularly critical aspect to be considered when designing operating machines of the above-noted kind relates to the reliability of the hermetic sealing of the rotating members; in fact, the sealing gaskets used for the rotor assembly are generally subject to frictional wear, which causes the same gaskets to undergo rapid deterioration and, as a result, a corresponding decay in the sealing properties thereof; this gives rise to a possibility for the machine to start malfunctioning due to leakages, seepages, pressure drops or losses, and the like.

US 2005/0147512 discloses a rotary pump for use in the medical field, in particular in connection with applications in the cardiovascular sector as a means to assist in the pumping function of the heart of a patient. This pump includes an impeller supported by magnetic bearings of an axial type, which consist of a magnet incorporated in the impeller and two mutually opposed stator windings. The magnetic field created by said magnet and said windings causes the impeller to, so to say, float within the body containing it.

Although being particularly compact in volume, even considering the applications it is intended for, the constructive concepts at the basis of a pump of this kind are such as to enable to achieve output power levels certainly suitable to an application in the medical field, but totally inadequate to applications in industry products such as home appliances and the like.

Moreover, the presence of electromagnetic bearings implies a need to constantly check and control in a very accurate manner the power supply to the stator windings so as to keep the impeller duly floating between the two windings. In fact, even a quite slight variation in the potential between such two windings would cause the impeller, which incorporates the magnet, to be attracted towards either one or the other winding, thereby possibly impairing the correct operation of the pump.

Another drawback lies in the fact that the inlet pipe of the pump extends through a stator winding, so that the diameter of such pipe is subject to strict dimensional constraints. As a result, the actual flow rate of the working fluid is limited by such dimensional constraints, and this is the reason why the pump is practically suited to applications involving a low flow-rate of fluid, as this is in fact the case in the medical field.

FR 2734605 discloses an electric water-pump for domestic appliances which includes an electric motor which drives a turbine of the electric pump. The electric motor is a permanent-magnet type motor and the turbine is associated directly with the rotor in such a way that a compact structure is achieved, in which the usual rotor of the motor is part of the turbine, the latter enclosing the electromotor rotor.

DE 19646617 discloses a pump which has a pump wheel rotor in a pump chamber and a pole system in a pole chamber with motor windings. Both chambers are hermetically sealed each other. The pole chamber is mounted in a heat conducting metal housing and the pole system is held radially, axially and rotationally fixed with the motor windings, pole cores and a short circuit ring. The motor windings are connected via cables to a circuit board mounted in an auxiliary chamber in contact with the metal housing wall.

Both these prior art embodiments feature a rotor and a turbine, or pump wheel, rotating about an axis defined by a pin perpendicularly extending from a central portion of the stator assembly, or pole chamber, into a housing in the turbine or pump wheel. The pin, acting as a guiding and controlling means of the rotary motion of the rotor and the turbine in respect of the stator, has a lower portion housed in a deep recess of a flange hermetically separating the rotor from the stator and an upper portion housed in a recess of the turbine with the interposition of a cylindrical bearing. Such a construction implies that, in case of a small misalignment of the pin in respect to the rotational perpendicular axis, vibrations of a significant amount can occur in the rotating assembly, i.e. the rotor and the turbine, due to the high extension of the pin.

Further, for the same reason, few or no space is left in the stator, or pole chamber, for arranging electronic control circuits or devices, due to the presence of the lower portion of the pin and the related housing in the flange; this drawback is particularly felt when the pump has to be extremely compact, such as for instance its use in domestic appliances like dishwashers or washing machines.

It is therefore a main object of the present invention to provide a pump of the afore-noted kind, which is effective in doing away with the drawbacks and limitations of prior-art pumps as stated above.

Within this general aim, it is a purpose of the present invention to provide an operating machine, in particular a motor-driven pump with an axial motor arrangement, wherein the dimensions, in particular the axial dimension, are considerably reduced while keeping the capability to supply power output levels suitable to industry applications.

Another purpose of the present invention is to provide an operating machine wherein any sealing members between fluid and rotating parts, in particular between the fluid and the motor, can be eliminated while anyway ensuring the required hermetic sealing of the same rotating parts.

A further purpose of the present invention is to provide an operating machine wherein the hermetic sealing between the rotating parts and the working fluid is ensured to stay unaltered and fully reliable in the long term, so that the causes of frictional wear are prevented or significantly reduced.

Yet another purpose of the present invention is to simplify the control of power supply to the electric motor while at the same time reliably ensuring correct operation of the machine.

A further purpose is to provide an operating machine extremely compact and able to house inside the stator compartment the required electronic control circuits and devices.

Another purpose is to provide an operating machine wherein vibrations are prevented or considerably reduced.

Another, equally important purpose of the present invention is to provide an operating machine of the above-noted kind at fully competitive costs with the use of readily available techniques, tools and machinery.

According to the present invention, these aims, along with further ones that shall become apparent from the following disclosure, are reached in an operating machine, in particular a motor-driven pump with an axial motor arrangement, as defined in claim 1.

Further characteristics of the operating machine according to the present invention are defined in the dependent claims.

Features and advantages of the present invention will anyway be more readily understood from the description of a preferred, although not sole embodiment that is given below by way of non-limiting example with reference to the accompanying drawings, in which:

FIG. 1 is a perspective view of an operating machine according to the present invention;

FIG. 2 is an exploded perspective view of main parts forming the operating machine shown in FIG. 1;

FIG. 3 is a cross-sectional view along a diametrical plane of a component part of the operating machine shown in FIG. 1;

FIG. 4 is a plan view of the operating machine shown in FIG. 1;

FIG. 5 is a cross-sectional view of the operating machine shown in FIG. 4 taken along plane V-V;

FIG. 6 is an exploded perspective view of a second embodiment of an operating machine according to the present invention;

FIGS. 7 and 8 are views of a third embodiment of an operating machine according to the present invention;

FIGS. 9 and 10 are views of a fourth embodiment of an operating machine according to the present invention;

FIG. 11 is a view of a fifth embodiment of an operating machine according to the present invention;

FIG. 12 is a view of a sixth embodiment of an operating machine according to the present invention;

FIG. 13 is a view of a seventh embodiment of an operating machine according to the present invention;

FIG. 14 is an exploded perspective view of some component parts of the embodiment of FIG. 13;

FIG. 15 is a cross-sectional view of the component parts shown in FIG. 14 taken along a diametral plane.

With reference to above-listed Figures, the inventive operating machine, such as a motor-driven pump with an axial motor arrangement, comprises a diffuser 1 with an inflow 2 and at least one outflow 3 for a working fluid, a rotor assembly 18, which essentially comprises an impeller 4 and an axially magnetized permanent-magnet rotor 5 that is associated in a firmly joined manner to the impeller 4; a flange 6 separates the rotor assembly 18 from a stator assembly 7 consisting essentially of a multipolar stator that comprises a plurality of magnetic poles 8 connected to a yoke 9, as well as a plurality of stator coils 10, each one of which being wound round a respective magnetic pole 8. Each such stator coil 10 is energized via an electrical connection 11 connected to a base plate 12; the stator 7 is housed within a body 13 provided with connectors 14 connected, on one side thereof, to the base plate 12; on the opposite side, the connectors 14 are adapted to be connected—with the aid of means known in the art—to both the power-supply line and the control signals.

Advantageously an electronic circuit 15, properly arranged on the base plate 12, can be provided for controlling the power supply to the stator assembly 7.

Appropriate guide means for guiding the rotary motion of the impeller 4 along an axis A extending perpendicularly to the rotor 5 are provided between the impeller 4 and the flange 6; the guide means are arranged so as to leave substantially free a central region of the stator assembly 7; in such a way, the electronic circuit 15, or any other devices that may be required for the functioning of the operating machine, can be easily arranged on the base plate 12 and housed in the stator assembly 7 in order to achieve an extremely compact structure of the operating machine.

In the embodiment of FIGS. 1 to 5, as well as in the subsequent embodiments of FIGS. 6, 7-8, 9-10, 11 and 12 which will be disclosed more in detail below, the guide means extend downwardly along the axis A protruding from the flange 6 and the rotor assembly 18 toward the stator assembly 7 substantially up to a region defined by a top portion of the multipolar stator, in particular a top portion of the magnetic poles 8.

Such guide means may consist of a circular groove 16, which may for instance be provided on the flange 6, and which is capable of engaging a corresponding circular rim provided on the impeller 4 or the rotor 5, as it shall be described in more detail below. It shall be of course understood that a reversed arrangement of the described groove-rim engagement has to be considered fully equivalent to the purposes of the present invention.

According to a preferred embodiment, which is illustrated in FIG. 3, the rotor assembly 18 is formed by overmoulding the impeller 4 onto the rotor 5, whereby a thin disk 19 resting on the flange 6 and adapted to support the rotor 5 is obtained on the impeller 4; a circular rim 17 protruding from the disk 19 extends towards the groove 16 on the flange 6.

Advantageously, the circular groove 16 is obtained in one piece with the flange 6 and the circular rim is obtained in one piece with the impeller 4.

It shall be appreciated that different embodiments of the guide means may of course be contemplated without departing from the scope of the present invention as defined in claim 1.

Advantageously, the rotor 5 may be formed of a portion of permanent magnets 21 and a portion made of ferromagnetic material 22, so as to improve the efficiency or increase the power output of the operating machine.

The operating machine according to the present invention operates as follows: once that the stator coils 10 are electrically energized via the connectors 14 and the related electrical connections 11, the multipolar stator 7 imparts a rotary motion to the permanent-magnet rotor 5 which, in turn, causes the impeller 4 to rotate, being the rotor 5 firmly joined to the impeller 4.

The rotor 5 is driven into rotation and attracted by the electromagnetic force exerted by the stator 7, so that the rotor assembly 18, which comprises the impeller 4 and the rotor 5, is caused to rotate while slidably resting on the flange 6; the rotary motion of the rotor assembly 18 is guided by the guide means situated between the same rotor assembly 18 and the flange 6. In this particular case, this is achieved by the engagement between the groove 16 in the flange 6 and the circular rim 17 of the impeller 4, as described above.

Fully apparent from the above description is therefore the ability of the present invention to effectively reach the aims and advantages cited afore, by in fact providing an operating machine, in particular a motor-driven pump with an axial motor arrangement, which is effective in doing away with the drawbacks of prior-art.

In the first place, the above-cited operating machine according to the present invention allows to sensibly reduce the overall dimensions, in particular the overall axial dimensions of the machine, thanks to the fact that the rotor 5 is incorporated in the impeller 4, as well as to the fact that there is no need to provide any rotating sealing member between the working fluid and the rotor assembly 18. In fact, the rotary motion of the rotor 5 driven by the electromagnetic field created by the stator assembly 7 causes the transmission of such rotary motion to the impeller 4, thereby allowing to eliminate the conventional motor shaft used for motion transmission to the impeller. Therefore the flange 6 can be made as a solid piece without any aperture in it, since no aperture is in fact required any longer to allow a motor shaft passing therethrough, as this is usually needed in the prior art and, as a consequence, no rotary sealing means are longer required to prevent working fluid from possibly seeping therethrough.

The elimination of such rotary sealing means makes it furthermore possible to prevent another primary cause of malfunctioning of the machine due to the wear and tear of such sealing members In fact, hermetic sealing is solely required at the joint between the flange 6 and the diffuser 1 and, therefore, between parts that do not move relative to each other, whereby it is possible to use solely static sealing members which are not subject to frictional wear. Optimum fluid-tightness properties of the machine are in this way reliably ensured in the long-term.

In addition, the sliding-type support of the rotor assembly 18 on the flange 6 introduces a considerable simplification in the manner in which the power supply to the stator assembly 7 can be controlled; in fact, the attraction force of the magnetic field is unidirectional and oriented in a direction in which it attracts the rotor assembly 18 towards the flange 6.

A further advantage lies in the possibility to incorporate the electrical connections and even a possibly provided electronic control circuit 15 within the stator assembly 7 thanks to an improved distribution of internal volumes which allows to save a considerable amount of space in the final application.

It shall be appreciated that the present invention may of course be the subject of a number of further embodiments and modifications without departing from the scope of the invention as defined in claim 1.

By way of example, a second embodiment of the operating machine according to the present invention is illustrated in FIG. 6, wherein the stator assembly 7A solely comprises a plurality of stator coils 10A, each one of which being wound so as to form a respective magnetic pole. Such an embodiment is particularly suitable in the case of operating machines in which the power rating required for the specific industrial application is not high, so that the magnetic field created by the sole coils 10A proves adequate to ensure such power level.

In a third embodiment of the operating machine according to the present invention, as illustrated in FIGS. 7 and 8, the rotor assembly 18B comprises a rotor 5B that is firmly joined on its lower side to the impeller 4B by methods known in the art, such as by welding, bonding or the like; a circular rim 17B which protrudes on the lower side of the rotor 5B forms, together with the groove 16B in the flange 6B, the guide means for the rotary motion of the impeller 4B.

FIGS. 9 and 10 illustrate a fourth embodiment, in which a heating element 20, such as for instance an electric resistance heater, an induction heater or the like, is added to an operating machine provided as described above. The heating element 20 is wound—either inside or outside—round the diffuser 1C, or it may even be incorporated therein, and is advantageously energized via the electrical connection 11C that ensures the power supply to the coils 100 and/or the possibly provided electronic control circuit 15C. Even the appropriately provided cut-off devices and the sensors used to control and protect the heating element 20 against overheating may be energized via the same electrical connection 11C and/or the possibly provided electronic control circuit 15C.

A protective cover 23 is preferably provided to both protect and thermally insulate the heating element 20 from the outside environment.

Incorporating a heating element 20 in an operating machine made and embodied as described above makes it possible to transfer heat from the rotor to the working fluid so as to increase the thermodynamic efficiency of the system whenever the working fluid is required to be heated. In addition, the power rating of the same heating element can be reduced by taking advantage of using a part of the heat generated by the rotor.

A fifth embodiment of an operating machine according to the present invention is illustrated in FIG. 11, wherein the multipolar stator in this case comprises a single coil 10D and the flux is conveyed via a plurality of magnetic poles 8D, preferably made of a ferromagnetic material, which close up in an alternate sequence on the upper side of the coil 10D so as to form an alternate pattern of north and south poles. Advantageously, in a particularly cost-effective configuration thereof, the poles may be provided in the form of appropriately cut and bent sheet-metal.

With this further embodiment, particularly suitable for applications requiring a reduced power rating, such as in the case of, for example, drain pumps, low-cost air circulation pumps for ovens, cookers or stoves, circulation pumps for small water treatment plants, or the like, a further and significant reduction in manufacturing costs is obtained, thanks to an extremely simplified construction of the related component parts, while anyway ensuring an effective and reliable separation of the working fluid from the dry portion of the machine without any use of rotary sealing means.

A sixth embodiment—similar to the previous embodiment—of an operating machine according to the present invention is illustrated in FIG. 12, wherein two coils 10E, 10′E are provided, which are arranged concentrically relative to each other and are partially enclosed by a first and a second plurality of magnetic poles 8E, 8′E, respectively. Again, these magnetic poles close up in an alternate sequence on the upper sides of the respective coils 10E, 10′E so as to form respective alternate patterns of north and south poles.

A seventh embodiment, as shown in FIGS. 13 to 15, comprises a diffuser 1F with an inflow 2F and at least one outflow 3F for a working fluid, a rotor assembly 18F, which essentially comprises an impeller 4F and an axially magnetized permanent-magnet rotor 5F that is associated in a firmly joined manner to the impeller 4F, preferably overmoulded or permanently attached by, for instance, welding, bonding or the like; a flange 6F separates the rotor assembly 18F from a stator assembly 7F consisting essentially of a multipolar stator that comprises a plurality of magnetic poles 8F connected to a yoke 9F, as well as a plurality of stator coils 10F, each one of which being wound round a respective magnetic pole 8F. Each such stator coil 10F is energized via an electrical connection 11F connected to a base plate 12F; the stator 7F is housed within a body, advantageously formed by a first half body 13F and a second half body 13′F, provided with connectors (not shown) suitable to be connected, on one side, to the base plate 12F and, on the opposite side, to both the power-supply line and the control signals.

Advantageously an electronic control circuit or an electronic control board, properly arranged on the base plate 12F, can be provided for controlling the power supply to the stator assembly 7F, as exemplified in the previous embodiments.

Appropriate guide means for guiding the rotary motion of the impeller 4F along the axis A extending perpendicularly to the rotor 5F are provided between the impeller 4F and the flange 6F; the guide means are arranged so as to leave substantially free a central region of the stator assembly 7F; in such a way, an electronic circuit, or any other devices that may be required for the functioning of the operating machine, can be easily arranged on the base plate 12F and housed in the stator assembly 7F in order to achieve an extremely compact structure of the operating machine, as previously described.

In the embodiment of FIGS. 13 to 15 the guide means extend upwardly along the axis A from a central region of the flange 6F and the rotor assembly 18F towards an upper portion of the impeller 4F.

Such guide means comprise a pin 24F which extends upwardly from a central region of the flange 6F and it is adapted to engage with a corresponding recess 29F in the impeller 4F which extends from a central base portion towards an upper portion of the impeller 4F.

Advantageously, the pin 29F is obtained in one piece with the flange 6.

In order to reduce friction between the rotor assembly 18F and the flange 6F, antifriction means are advantageously provided; such antifriction means may comprise axial antifriction means, for instance constituted by a bush 26F made of an antifriction material, interposed between the pin 24F and the recess 29F in the impeller 4F, and radial antifriction means constituted, for instance, by a washer 27F, preferably also made of an antifriction material, housed in a recessed seat 25F of the flange 6F; the washer 27F may be directly in contact with the bush 26F, as shown in FIG. 15, or with a central portion of the base of the impeller 4F.

It shall be appreciated that the materials used, as well as the shape and the dimensions of the various parts, may of course each time be selected so as to more appropriately meet the particular requirements or suit the particular application. 

1. Operating machine, in particular a motor-driven pump with an axial motor arrangement, comprising a rotor assembly (18; 18A; 18B; 18C; 18D; 18E; 18F) and a stator assembly (7; 7A; 7B; 7C; 7D; 7E; 7F), said rotor assembly including an impeller (4; 4A; 4B; 4C; 4D; 4E; 4F) and a permanent-magnet rotor (5; 5A; 5B; 5C; 5D; 5E; 5F) firmly associated to said impeller (4; 4A; 4B; 4C; 4D; 4E; 4F), characterized in that said stator assembly (7; 7A; 7B; 7C; 7D; 7E; 7F) includes a single multipolar stator (8, 9, 10; 10A; 8B, 9B, 10B; 8C, 9C, 10C; 8D, 9D, 10D; 8E, 8′E, 9E, 10E, I CE; 8F, 9F, 10F) interacting with said rotor (5; 5A; 5B; 5C; 5D; 5E; 5F) to impart a rotary motion to said impeller (4; 4A; 4B; 4C; 4D; 4E; 4F) along an axis (A) perpendicular to said rotor (5; 5A; 5B; 5C; 5D; 5E; 5F), said rotor assembly (18; 18A; 18B; 18C; 18D; 18E; 18F) being rotatably supported by a flange (6; 6A; 6B; 6C; 6D; 6E; 6F) adapted to separate said rotor assembly (18; 18A; 18B; 18C; 18D; 18E; 18F) from said stator assembly (7; 7A; 7B; 7C; 7D; 7E; 7F), guide means (16, 17; 16A; 16B, 17B; 16C; 16D; 16E; 24F, 29F) being provided between said rotor assembly (18; 18A; 18B; 18C; 18D; 18E; 18F) and said flange (6; 6A; 6B; 6C; 6D; 6E; 6F) to guide the rotary motion of said impeller (4; 4A; 4B; 4C; 4D; 4E; 4F) about said axis (A).
 2. Operating machine according to claim 1, wherein said guide means (16, 17; 16A; 16B, 17B; 16C; 16D; 16E; 24F, 29F) extend longitudinally along said axis (A) perpendicular to said rotor (5; 5A; 5B; 5C; 5D; 5E; 5F) leaving substantially free a central region of said stator assembly (7; 7A; 7B; 7C; 7D; 7E; 7F).
 3. Operating machine according to claim 2, wherein said guide means (16, 17; 16A; 16B, 17B; 16C; 16D; 16E) extend along said axis (A) protruding from said flange (6; 6A; 6B; 6C; 6D; 6E) and said rotor assembly (18; 18A; 18B; 18C; 18D; 18E; 18F) towards said stator assembly (7; 7A; 7B; 7C; 7D; 7E) substantially up to a region defined by an upper portion of said multipolar stator (8, 9, 10; 10A; 8B, 9B, 10B; 8C, 9C, 10C; 8D, 9D, 10D; 8E, 8′E, 9E, 10E, 10′E).
 4. Operating machine according to claim 3, wherein said guide means (16, 17) comprise a circular groove (16) provided on said flange (6) and adapted to engage a corresponding circular rim (17) extending from said impeller (4) towards said flange (6).
 5. Operating machine according to claim 4, wherein said circular groove (16) is obtained in one piece with said flange (6) and said circular rim (17) is obtained in one piece with said impeller (4).
 6. Operating machine according to claim 2, wherein said guide means (24F, 29F) extend along said axis (A) from a central region of said flange (6F) and said rotor assembly (18F) towards an upper portion of said impeller (4F).
 7. Operating machine according to claim 6, wherein said guide means comprise a pin (24F) extending from a central region of said flange (6F) and adapted to engage a corresponding recess (29F) in said impeller (4F), said recess (29F) extending from a central base portion of said impeller (4F) towards said upper portion of said impeller (4F).
 8. Operating machine according to claim 7, wherein antifriction means (26F, 27F) are interposed between said pin (24F) and said recess (29F).
 9. Operating machine according to claim 7, wherein said pin (24F) is obtained in one piece with said flange (6F).
 10. Operating machine according to claim 1, wherein said impeller (4) is formed by overmoulding onto said rotor (5).
 11. Operating machine according to claim 1, wherein said said rotor (5B) is firmly joined with said impeller (4B).
 12. Operating machine according to claim 3, wherein said guide means (16B, 17B) comprise a circular groove (16B) provided on said flange (6B) and adapted to engage a corresponding circular rim (17B) extending from said rotor (5B) towards said flange (6B).
 13. Operating machine according to claim 1, wherein said rotor (5; 5A; 5B; 5C; 5D; 5E; 5F) is axially magnetized.
 14. Operating machine according to claim 1, wherein said multipolar stator comprises a plurality of magnetic poles (8; 8B; 8C; 8F) connected to a yoke (9; 9B; 9C; 9F) and a plurality of stator coils (10; 1 OB; 10C; 10F), each stator coil of said plurality of stator coils (10; 10B; 10C; 10F) being wound round a respective magnetic pole of said plurality of magnetic poles (8; 8B; 8C; 8F).
 15. Operating machine according to claim 1, wherein said multipolar stator comprises a plurality of stator coils (10A), each stator coil of said plurality of stator coils (10A) being wound to form a respective magnetic pole.
 16. Operating machine according to claim 1, wherein said multipolar stator comprises at least one stator coil (10D; 10E, 10′E) at least partially enclosed by a plurality of magnetic poles (8D; 8E, 8′E) that close up in an alternate sequence on the upper side of said at least one stator coil (10D; 10E, 10′E) to form a respective plurality of alternate patterns of north and south poles.
 17. Operating machine according to claim 16, wherein said multipolar stator comprises at least a first stator coil (10E) and a second stator coil (10′E), said first stator coil (10E) and second stator coil (10′E) being at least partially enclosed by a first plurality of magnetic poles (8E) and a second plurality of magnetic poles (8′E), respectively, said first stator coil (10E) and said second stator coil (10′E) and, respectively, said first plurality of magnetic poles (8E) and said second plurality of magnetic poles (8′E) being concentrically arranged relative to each other.
 18. Operating machine according to claim 1, wherein said rotor assembly (18; 18A; 18B; 18C; 18D; 18E; 18F) is contained in a diffuser (1 ;1A; 1 B; 1 C; 1 D; 1 E; 1 F) provided with an inflow aperture (2; 2A; 2B; 2C; 2D; 2E; 2F) and at least one outflow aperture (3; 3A; 3B; 3C; 3D; 3E; 3F), said diffuser (1 ; 1A; 1 B; 1 C; 1 D; 1 E; 1 F) being sealingly connected to said flange (6; 6A; 6B; 6C; 6D; 6E; 6F).
 19. Operating machine according to claim 18, wherein at least one heating element (20) is associable to said diffuser (1 C).
 20. Operating machine according to claim 19, wherein said heating element (20) is wound either inside or outside on said diffuser (1 C) or incorporated therein. 